services/keep-web/handler.go

   1 // Copyright (C) The Arvados Authors. All rights reserved.
   2 //
   3 // SPDX-License-Identifier: AGPL-3.0
   4
   5 package main
   6
   7 import (
   8         "encoding/json"
   9         "errors"
  10         "fmt"
  11         "html"
  12         "html/template"
  13         "io"
  14         "net/http"
  15         "net/url"
  16         "os"
  17         "sort"
  18         "strconv"
  19         "strings"
  20         "sync"
  21
  22         "git.curoverse.com/arvados.git/sdk/go/arvados"
  23         "git.curoverse.com/arvados.git/sdk/go/arvadosclient"
  24         "git.curoverse.com/arvados.git/sdk/go/auth"
  25         "git.curoverse.com/arvados.git/sdk/go/health"
  26         "git.curoverse.com/arvados.git/sdk/go/httpserver"
  27         "git.curoverse.com/arvados.git/sdk/go/keepclient"
  28         "golang.org/x/net/webdav"
  29 )
  30
  31 type handler struct {
  32         Config        *Config
  33         clientPool    *arvadosclient.ClientPool
  34         setupOnce     sync.Once
  35         healthHandler http.Handler
  36         webdavLS      webdav.LockSystem
  37 }
  38
  39 // parseCollectionIDFromDNSName returns a UUID or PDH if s begins with
  40 // a UUID or URL-encoded PDH; otherwise "".
  41 func parseCollectionIDFromDNSName(s string) string {
  42         // Strip domain.
  43         if i := strings.IndexRune(s, '.'); i >= 0 {
  44                 s = s[:i]
  45         }
  46         // Names like {uuid}--collections.example.com serve the same
  47         // purpose as {uuid}.collections.example.com but can reduce
  48         // cost/effort of using [additional] wildcard certificates.
  49         if i := strings.Index(s, "--"); i >= 0 {
  50                 s = s[:i]
  51         }
  52         if arvadosclient.UUIDMatch(s) {
  53                 return s
  54         }
  55         if pdh := strings.Replace(s, "-", "+", 1); arvadosclient.PDHMatch(pdh) {
  56                 return pdh
  57         }
  58         return ""
  59 }
  60
  61 var urlPDHDecoder = strings.NewReplacer(" ", "+", "-", "+")
  62
  63 // parseCollectionIDFromURL returns a UUID or PDH if s is a UUID or a
  64 // PDH (even if it is a PDH with "+" replaced by " " or "-");
  65 // otherwise "".
  66 func parseCollectionIDFromURL(s string) string {
  67         if arvadosclient.UUIDMatch(s) {
  68                 return s
  69         }
  70         if pdh := urlPDHDecoder.Replace(s); arvadosclient.PDHMatch(pdh) {
  71                 return pdh
  72         }
  73         return ""
  74 }
  75
  76 func (h *handler) setup() {
  77         h.clientPool = arvadosclient.MakeClientPool()
  78
  79         keepclient.RefreshServiceDiscoveryOnSIGHUP()
  80
  81         h.healthHandler = &health.Handler{
  82                 Token:  h.Config.ManagementToken,
  83                 Prefix: "/_health/",
  84         }
  85
  86         // Even though we don't accept LOCK requests, every webdav
  87         // handler must have a non-nil LockSystem.
  88         h.webdavLS = &noLockSystem{}
  89 }
  90
  91 func (h *handler) serveStatus(w http.ResponseWriter, r *http.Request) {
  92         status := struct {
  93                 cacheStats
  94         }{
  95                 cacheStats: h.Config.Cache.Stats(),
  96         }
  97         json.NewEncoder(w).Encode(status)
  98 }
  99
 100 // updateOnSuccess wraps httpserver.ResponseWriter. If the handler
 101 // sends an HTTP header indicating success, updateOnSuccess first
 102 // calls the provided update func. If the update func fails, a 500
 103 // response is sent, and the status code and body sent by the handler
 104 // are ignored (all response writes return errors).
 105 type updateOnSuccess struct {
 106         httpserver.ResponseWriter
 107         update     func() error
 108         sentHeader bool
 109         dropBody   bool
 110 }
 111
 112 var errUpdateFailed = errors.New("update failed")
 113
 114 func (uos *updateOnSuccess) Write(p []byte) (int, error) {
 115         if uos.dropBody {
 116                 return 0, errUpdateFailed
 117         }
 118         if !uos.sentHeader {
 119                 uos.WriteHeader(http.StatusOK)
 120         }
 121         return uos.ResponseWriter.Write(p)
 122 }
 123
 124 func (uos *updateOnSuccess) WriteHeader(code int) {
 125         if !uos.sentHeader {
 126                 if code >= 200 && code < 400 {
 127                         if err := uos.update(); err != nil {
 128                                 http.Error(uos.ResponseWriter, err.Error(), http.StatusInternalServerError)
 129                                 uos.dropBody = true
 130                                 return
 131                         }
 132                 }
 133                 uos.sentHeader = true
 134         }
 135         uos.ResponseWriter.WriteHeader(code)
 136 }
 137
 138 var (
 139         webdavMethod = map[string]bool{
 140                 "DELETE":   true,
 141                 "MKCOL":    true,
 142                 "MOVE":     true,
 143                 "OPTIONS":  true,
 144                 "PROPFIND": true,
 145                 "PUT":      true,
 146                 "RMCOL":    true,
 147         }
 148         browserMethod = map[string]bool{
 149                 "GET":  true,
 150                 "HEAD": true,
 151                 "POST": true,
 152         }
 153 )
 154
 155 // ServeHTTP implements http.Handler.
 156 func (h *handler) ServeHTTP(wOrig http.ResponseWriter, r *http.Request) {
 157         h.setupOnce.Do(h.setup)
 158
 159         var statusCode = 0
 160         var statusText string
 161
 162         remoteAddr := r.RemoteAddr
 163         if xff := r.Header.Get("X-Forwarded-For"); xff != "" {
 164                 remoteAddr = xff + "," + remoteAddr
 165         }
 166
 167         w := httpserver.WrapResponseWriter(wOrig)
 168         defer func() {
 169                 if statusCode == 0 {
 170                         statusCode = w.WroteStatus()
 171                 } else if w.WroteStatus() == 0 {
 172                         w.WriteHeader(statusCode)
 173                 } else if w.WroteStatus() != statusCode {
 174                         httpserver.Log(r.RemoteAddr, "WARNING",
 175                                 fmt.Sprintf("Our status changed from %d to %d after we sent headers", w.WroteStatus(), statusCode))
 176                 }
 177                 if statusText == "" {
 178                         statusText = http.StatusText(statusCode)
 179                 }
 180                 httpserver.Log(remoteAddr, statusCode, statusText, w.WroteBodyBytes(), r.Method, r.Host, r.URL.Path, r.URL.RawQuery)
 181         }()
 182
 183         if strings.HasPrefix(r.URL.Path, "/_health/") && r.Method == "GET" {
 184                 h.healthHandler.ServeHTTP(w, r)
 185                 return
 186         }
 187
 188         if method := r.Header.Get("Access-Control-Request-Method"); method != "" && r.Method == "OPTIONS" {
 189                 if !browserMethod[method] && !webdavMethod[method] {
 190                         statusCode = http.StatusMethodNotAllowed
 191                         return
 192                 }
 193                 w.Header().Set("Access-Control-Allow-Headers", "Authorization, Content-Type, Range")
 194                 w.Header().Set("Access-Control-Allow-Methods", "DELETE, GET, MKCOL, MOVE, OPTIONS, POST, PROPFIND, PUT, RMCOL")
 195                 w.Header().Set("Access-Control-Allow-Origin", "*")
 196                 w.Header().Set("Access-Control-Max-Age", "86400")
 197                 statusCode = http.StatusOK
 198                 return
 199         }
 200
 201         if !browserMethod[r.Method] && !webdavMethod[r.Method] {
 202                 statusCode, statusText = http.StatusMethodNotAllowed, r.Method
 203                 return
 204         }
 205
 206         if r.Header.Get("Origin") != "" {
 207                 // Allow simple cross-origin requests without user
 208                 // credentials ("user credentials" as defined by CORS,
 209                 // i.e., cookies, HTTP authentication, and client-side
 210                 // SSL certificates. See
 211                 // http://www.w3.org/TR/cors/#user-credentials).
 212                 w.Header().Set("Access-Control-Allow-Origin", "*")
 213                 w.Header().Set("Access-Control-Expose-Headers", "Content-Range")
 214         }
 215
 216         arv := h.clientPool.Get()
 217         if arv == nil {
 218                 statusCode, statusText = http.StatusInternalServerError, "Pool failed: "+h.clientPool.Err().Error()
 219                 return
 220         }
 221         defer h.clientPool.Put(arv)
 222
 223         pathParts := strings.Split(r.URL.Path[1:], "/")
 224
 225         var stripParts int
 226         var targetID string
 227         var tokens []string
 228         var reqTokens []string
 229         var pathToken bool
 230         var attachment bool
 231         credentialsOK := h.Config.TrustAllContent
 232
 233         if r.Host != "" && r.Host == h.Config.AttachmentOnlyHost {
 234                 credentialsOK = true
 235                 attachment = true
 236         } else if r.FormValue("disposition") == "attachment" {
 237                 attachment = true
 238         }
 239
 240         if targetID = parseCollectionIDFromDNSName(r.Host); targetID != "" {
 241                 // http://ID.collections.example/PATH...
 242                 credentialsOK = true
 243         } else if r.URL.Path == "/status.json" {
 244                 h.serveStatus(w, r)
 245                 return
 246         } else if len(pathParts) >= 1 && strings.HasPrefix(pathParts[0], "c=") {
 247                 // /c=ID[/PATH...]
 248                 targetID = parseCollectionIDFromURL(pathParts[0][2:])
 249                 stripParts = 1
 250         } else if len(pathParts) >= 2 && pathParts[0] == "collections" {
 251                 if len(pathParts) >= 4 && pathParts[1] == "download" {
 252                         // /collections/download/ID/TOKEN/PATH...
 253                         targetID = parseCollectionIDFromURL(pathParts[2])
 254                         tokens = []string{pathParts[3]}
 255                         stripParts = 4
 256                         pathToken = true
 257                 } else {
 258                         // /collections/ID/PATH...
 259                         targetID = parseCollectionIDFromURL(pathParts[1])
 260                         tokens = h.Config.AnonymousTokens
 261                         stripParts = 2
 262                 }
 263         }
 264
 265         if targetID == "" {
 266                 statusCode = http.StatusNotFound
 267                 return
 268         }
 269
 270         formToken := r.FormValue("api_token")
 271         if formToken != "" && r.Header.Get("Origin") != "" && attachment && r.URL.Query().Get("api_token") == "" {
 272                 // The client provided an explicit token in the POST
 273                 // body. The Origin header indicates this *might* be
 274                 // an AJAX request, in which case redirect-with-cookie
 275                 // won't work: we should just serve the content in the
 276                 // POST response. This is safe because:
 277                 //
 278                 // * We're supplying an attachment, not inline
 279                 //   content, so we don't need to convert the POST to
 280                 //   a GET and avoid the "really resubmit form?"
 281                 //   problem.
 282                 //
 283                 // * The token isn't embedded in the URL, so we don't
 284                 //   need to worry about bookmarks and copy/paste.
 285                 tokens = append(tokens, formToken)
 286         } else if formToken != "" && browserMethod[r.Method] {
 287                 // The client provided an explicit token in the query
 288                 // string, or a form in POST body. We must put the
 289                 // token in an HttpOnly cookie, and redirect to the
 290                 // same URL with the query param redacted and method =
 291                 // GET.
 292                 h.seeOtherWithCookie(w, r, "", credentialsOK)
 293                 return
 294         }
 295
 296         targetPath := pathParts[stripParts:]
 297         if tokens == nil && len(targetPath) > 0 && strings.HasPrefix(targetPath[0], "t=") {
 298                 // http://ID.example/t=TOKEN/PATH...
 299                 // /c=ID/t=TOKEN/PATH...
 300                 //
 301                 // This form must only be used to pass scoped tokens
 302                 // that give permission for a single collection. See
 303                 // FormValue case above.
 304                 tokens = []string{targetPath[0][2:]}
 305                 pathToken = true
 306                 targetPath = targetPath[1:]
 307                 stripParts++
 308         }
 309
 310         if tokens == nil {
 311                 if credentialsOK {
 312                         reqTokens = auth.NewCredentialsFromHTTPRequest(r).Tokens
 313                 }
 314                 tokens = append(reqTokens, h.Config.AnonymousTokens...)
 315         }
 316
 317         if len(targetPath) > 0 && targetPath[0] == "_" {
 318                 // If a collection has a directory called "t=foo" or
 319                 // "_", it can be served at
 320                 // //collections.example/_/t=foo/ or
 321                 // //collections.example/_/_/ respectively:
 322                 // //collections.example/t=foo/ won't work because
 323                 // t=foo will be interpreted as a token "foo".
 324                 targetPath = targetPath[1:]
 325                 stripParts++
 326         }
 327
 328         forceReload := false
 329         if cc := r.Header.Get("Cache-Control"); strings.Contains(cc, "no-cache") || strings.Contains(cc, "must-revalidate") {
 330                 forceReload = true
 331         }
 332
 333         var collection *arvados.Collection
 334         tokenResult := make(map[string]int)
 335         for _, arv.ApiToken = range tokens {
 336                 var err error
 337                 collection, err = h.Config.Cache.Get(arv, targetID, forceReload)
 338                 if err == nil {
 339                         // Success
 340                         break
 341                 }
 342                 if srvErr, ok := err.(arvadosclient.APIServerError); ok {
 343                         switch srvErr.HttpStatusCode {
 344                         case 404, 401:
 345                                 // Token broken or insufficient to
 346                                 // retrieve collection
 347                                 tokenResult[arv.ApiToken] = srvErr.HttpStatusCode
 348                                 continue
 349                         }
 350                 }
 351                 // Something more serious is wrong
 352                 statusCode, statusText = http.StatusInternalServerError, err.Error()
 353                 return
 354         }
 355         if collection == nil {
 356                 if pathToken || !credentialsOK {
 357                         // Either the URL is a "secret sharing link"
 358                         // that didn't work out (and asking the client
 359                         // for additional credentials would just be
 360                         // confusing), or we don't even accept
 361                         // credentials at this path.
 362                         statusCode = http.StatusNotFound
 363                         return
 364                 }
 365                 for _, t := range reqTokens {
 366                         if tokenResult[t] == 404 {
 367                                 // The client provided valid token(s), but the
 368                                 // collection was not found.
 369                                 statusCode = http.StatusNotFound
 370                                 return
 371                         }
 372                 }
 373                 // The client's token was invalid (e.g., expired), or
 374                 // the client didn't even provide one.  Propagate the
 375                 // 401 to encourage the client to use a [different]
 376                 // token.
 377                 //
 378                 // TODO(TC): This response would be confusing to
 379                 // someone trying (anonymously) to download public
 380                 // data that has been deleted.  Allow a referrer to
 381                 // provide this context somehow?
 382                 w.Header().Add("WWW-Authenticate", "Basic realm=\"collections\"")
 383                 statusCode = http.StatusUnauthorized
 384                 return
 385         }
 386
 387         kc, err := keepclient.MakeKeepClient(arv)
 388         if err != nil {
 389                 statusCode, statusText = http.StatusInternalServerError, err.Error()
 390                 return
 391         }
 392
 393         var basename string
 394         if len(targetPath) > 0 {
 395                 basename = targetPath[len(targetPath)-1]
 396         }
 397         applyContentDispositionHdr(w, r, basename, attachment)
 398
 399         client := &arvados.Client{
 400                 APIHost:   arv.ApiServer,
 401                 AuthToken: arv.ApiToken,
 402                 Insecure:  arv.ApiInsecure,
 403         }
 404         fs, err := collection.FileSystem(client, kc)
 405         if err != nil {
 406                 statusCode, statusText = http.StatusInternalServerError, err.Error()
 407                 return
 408         }
 409         if webdavMethod[r.Method] {
 410                 writing := !arvadosclient.PDHMatch(targetID)
 411                 if writing {
 412                         // Save the collection only if/when all
 413                         // webdav->filesystem operations succeed --
 414                         // and send a 500 error the modified
 415                         // collection can't be saved.
 416                         w = &updateOnSuccess{
 417                                 ResponseWriter: w,
 418                                 update: func() error {
 419                                         return h.Config.Cache.Update(client, *collection, fs)
 420                                 }}
 421                 }
 422                 h := webdav.Handler{
 423                         Prefix: "/" + strings.Join(pathParts[:stripParts], "/"),
 424                         FileSystem: &webdavFS{
 425                                 collfs:  fs,
 426                                 writing: writing,
 427                         },
 428                         LockSystem: h.webdavLS,
 429                         Logger: func(_ *http.Request, err error) {
 430                                 if os.IsNotExist(err) {
 431                                         statusCode, statusText = http.StatusNotFound, err.Error()
 432                                 } else if err != nil {
 433                                         statusCode, statusText = http.StatusInternalServerError, err.Error()
 434                                 }
 435                         },
 436                 }
 437                 h.ServeHTTP(w, r)
 438                 return
 439         }
 440
 441         openPath := "/" + strings.Join(targetPath, "/")
 442         if f, err := fs.Open(openPath); os.IsNotExist(err) {
 443                 // Requested non-existent path
 444                 statusCode = http.StatusNotFound
 445         } else if err != nil {
 446                 // Some other (unexpected) error
 447                 statusCode, statusText = http.StatusInternalServerError, err.Error()
 448         } else if stat, err := f.Stat(); err != nil {
 449                 // Can't get Size/IsDir (shouldn't happen with a collectionFS!)
 450                 statusCode, statusText = http.StatusInternalServerError, err.Error()
 451         } else if stat.IsDir() && !strings.HasSuffix(r.URL.Path, "/") {
 452                 // If client requests ".../dirname", redirect to
 453                 // ".../dirname/". This way, relative links in the
 454                 // listing for "dirname" can always be "fnm", never
 455                 // "dirname/fnm".
 456                 h.seeOtherWithCookie(w, r, r.URL.Path+"/", credentialsOK)
 457         } else if stat.IsDir() {
 458                 h.serveDirectory(w, r, collection.Name, fs, openPath, stripParts)
 459         } else {
 460                 http.ServeContent(w, r, basename, stat.ModTime(), f)
 461                 if r.Header.Get("Range") == "" && int64(w.WroteBodyBytes()) != stat.Size() {
 462                         // If we wrote fewer bytes than expected, it's
 463                         // too late to change the real response code
 464                         // or send an error message to the client, but
 465                         // at least we can try to put some useful
 466                         // debugging info in the logs.
 467                         n, err := f.Read(make([]byte, 1024))
 468                         statusCode, statusText = http.StatusInternalServerError, fmt.Sprintf("f.Size()==%d but only wrote %d bytes; read(1024) returns %d, %s", stat.Size(), w.WroteBodyBytes(), n, err)
 469
 470                 }
 471         }
 472 }
 473
 474 var dirListingTemplate = `<!DOCTYPE HTML>
 475 <HTML><HEAD>
 476   <META name="robots" content="NOINDEX">
 477   <TITLE>{{ .Collection.Name }}</TITLE>
 478   <STYLE type="text/css">
 479     body {
 480       margin: 1.5em;
 481     }
 482     pre {
 483       background-color: #D9EDF7;
 484       border-radius: .25em;
 485       padding: .75em;
 486       overflow: auto;
 487     }
 488     .footer p {
 489       font-size: 82%;
 490     }
 491     ul {
 492       padding: 0;
 493     }
 494     ul li {
 495       font-family: monospace;
 496       list-style: none;
 497     }
 498   </STYLE>
 499 </HEAD>
 500 <BODY>
 501 <H1>{{ .CollectionName }}</H1>
 502
 503 <P>This collection of data files is being shared with you through
 504 Arvados.  You can download individual files listed below.  To download
 505 the entire collection with wget, try:</P>
 506
 507 <PRE>$ wget --mirror --no-parent --no-host --cut-dirs={{ .StripParts }} https://{{ .Request.Host }}{{ .Request.URL }}</PRE>
 508
 509 <H2>File Listing</H2>
 510
 511 {{if .Files}}
 512 <UL>
 513 {{range .Files}}  <LI>{{.Size | printf "%15d  " | nbsp}}<A href="{{.Name}}">{{.Name}}</A></LI>{{end}}
 514 </UL>
 515 {{else}}
 516 <P>(No files; this collection is empty.)</P>
 517 {{end}}
 518
 519 <HR noshade>
 520 <DIV class="footer">
 521   <P>
 522     About Arvados:
 523     Arvados is a free and open source software bioinformatics platform.
 524     To learn more, visit arvados.org.
 525     Arvados is not responsible for the files listed on this page.
 526   </P>
 527 </DIV>
 528
 529 </BODY>
 530 `
 531
 532 type fileListEnt struct {
 533         Name string
 534         Size int64
 535 }
 536
 537 func (h *handler) serveDirectory(w http.ResponseWriter, r *http.Request, collectionName string, fs http.FileSystem, base string, stripParts int) {
 538         var files []fileListEnt
 539         var walk func(string) error
 540         if !strings.HasSuffix(base, "/") {
 541                 base = base + "/"
 542         }
 543         walk = func(path string) error {
 544                 dirname := base + path
 545                 if dirname != "/" {
 546                         dirname = strings.TrimSuffix(dirname, "/")
 547                 }
 548                 d, err := fs.Open(dirname)
 549                 if err != nil {
 550                         return err
 551                 }
 552                 ents, err := d.Readdir(-1)
 553                 if err != nil {
 554                         return err
 555                 }
 556                 for _, ent := range ents {
 557                         if ent.IsDir() {
 558                                 err = walk(path + ent.Name() + "/")
 559                                 if err != nil {
 560                                         return err
 561                                 }
 562                         } else {
 563                                 files = append(files, fileListEnt{
 564                                         Name: path + ent.Name(),
 565                                         Size: ent.Size(),
 566                                 })
 567                         }
 568                 }
 569                 return nil
 570         }
 571         if err := walk(""); err != nil {
 572                 http.Error(w, err.Error(), http.StatusInternalServerError)
 573                 return
 574         }
 575
 576         funcs := template.FuncMap{
 577                 "nbsp": func(s string) template.HTML {
 578                         return template.HTML(strings.Replace(s, " ", "&nbsp;", -1))
 579                 },
 580         }
 581         tmpl, err := template.New("dir").Funcs(funcs).Parse(dirListingTemplate)
 582         if err != nil {
 583                 http.Error(w, err.Error(), http.StatusInternalServerError)
 584                 return
 585         }
 586         sort.Slice(files, func(i, j int) bool {
 587                 return files[i].Name < files[j].Name
 588         })
 589         w.WriteHeader(http.StatusOK)
 590         tmpl.Execute(w, map[string]interface{}{
 591                 "CollectionName": collectionName,
 592                 "Files":          files,
 593                 "Request":        r,
 594                 "StripParts":     stripParts,
 595         })
 596 }
 597
 598 func applyContentDispositionHdr(w http.ResponseWriter, r *http.Request, filename string, isAttachment bool) {
 599         disposition := "inline"
 600         if isAttachment {
 601                 disposition = "attachment"
 602         }
 603         if strings.ContainsRune(r.RequestURI, '?') {
 604                 // Help the UA realize that the filename is just
 605                 // "filename.txt", not
 606                 // "filename.txt?disposition=attachment".
 607                 //
 608                 // TODO(TC): Follow advice at RFC 6266 appendix D
 609                 disposition += "; filename=" + strconv.QuoteToASCII(filename)
 610         }
 611         if disposition != "inline" {
 612                 w.Header().Set("Content-Disposition", disposition)
 613         }
 614 }
 615
 616 func (h *handler) seeOtherWithCookie(w http.ResponseWriter, r *http.Request, location string, credentialsOK bool) {
 617         if formToken := r.FormValue("api_token"); formToken != "" {
 618                 if !credentialsOK {
 619                         // It is not safe to copy the provided token
 620                         // into a cookie unless the current vhost
 621                         // (origin) serves only a single collection or
 622                         // we are in TrustAllContent mode.
 623                         w.WriteHeader(http.StatusBadRequest)
 624                         return
 625                 }
 626
 627                 // The HttpOnly flag is necessary to prevent
 628                 // JavaScript code (included in, or loaded by, a page
 629                 // in the collection being served) from employing the
 630                 // user's token beyond reading other files in the same
 631                 // domain, i.e., same collection.
 632                 //
 633                 // The 303 redirect is necessary in the case of a GET
 634                 // request to avoid exposing the token in the Location
 635                 // bar, and in the case of a POST request to avoid
 636                 // raising warnings when the user refreshes the
 637                 // resulting page.
 638                 http.SetCookie(w, &http.Cookie{
 639                         Name:     "arvados_api_token",
 640                         Value:    auth.EncodeTokenCookie([]byte(formToken)),
 641                         Path:     "/",
 642                         HttpOnly: true,
 643                 })
 644         }
 645
 646         // Propagate query parameters (except api_token) from
 647         // the original request.
 648         redirQuery := r.URL.Query()
 649         redirQuery.Del("api_token")
 650
 651         u := r.URL
 652         if location != "" {
 653                 newu, err := u.Parse(location)
 654                 if err != nil {
 655                         w.WriteHeader(http.StatusInternalServerError)
 656                         return
 657                 }
 658                 u = newu
 659         }
 660         redir := (&url.URL{
 661                 Host:     r.Host,
 662                 Path:     u.Path,
 663                 RawQuery: redirQuery.Encode(),
 664         }).String()
 665
 666         w.Header().Add("Location", redir)
 667         w.WriteHeader(http.StatusSeeOther)
 668         io.WriteString(w, `<A href="`)
 669         io.WriteString(w, html.EscapeString(redir))
 670         io.WriteString(w, `">Continue</A>`)
 671 }